1. Field of the Invention
The present invention generally relates to a semiconductor process, and more specifically to a semiconductor process, that performs a dry etching process to etch parts of a material layer and then performs a wet etching process to entirely remove the material layer.
2. Description of the Prior Art
With the trend of miniaturization of semiconductor devices dimensions, the scale of the gate, source and drain of a transistor decreases in accordance with the reduction of the critical dimension (CD). Due to physical limitations of the materials used, the decrease of the scale of the gate, source and drain also results in the decrease of the carriers that determine the magnitude of the current in the transistor, which can therefore adversely affect the performances of the transistor. Increasing the carrier mobility in order to boost up a MOS transistor is an important matter in the field of current semiconductor techniques.
One of the methods for applying stresses onto MOS transistors is a stress memorization technique (SMT), which enhances the carrier mobility. The processing steps of the stress memorization technique (SMT) include: (1) performing a pre-amorphization implant (PAI) process to form an amorphization layer on the surface of a silicon substrate; (2) depositing a stress layer on the silicon substrate; (3) performing a thermal treatment process to keep applying the stresses of the stress layer onto the silicon substrate; (4) removing the stress layer.
However, since the material of the stress layer is similar to that of a spacer beside a gate, the spacer will be damaged when the stress layer is removed. Thus, an inner spacer or a gate will be exposed, resulting in circuit leakages.